The present invention relates to signals filtering used in receivers and, more particularly, to method and device for adjacent channels operation based on downconverting the input signal to an IF signal, filtering the IF signal, and upconverting the filtered IF signal to the original frequency. The present invention is primarily directed to applications of telecommunication, however, the present invention clearly can be directed to other applications in a variety of other fields involving the use of standard RF transceiver which does not incorporate a high Q filter.
Basic principles and details relating to adjacent channels operation needed for properly understanding the present invention are provided herein. Complete theoretical descriptions, details, explanations, examples, and applications of these and related subjects and phenomena are readily available in standard references in the fields of telecommunication and signal filtering.
When operating adjacent and/or adjacent channels, there is a need for high Q filtering of the adjacent channels. The Q factor determines the sharpness of the response of the filter, corresponding to its degree of resonance. The greater the Q factor, the sharper the filter. When the Q factor is high, the frequency response is sharply focused around the resonance frequency.
Prior art solutions filter the signal within a RF transceiver. A significant general limitation of currently available solutions that are based on filtering the signal within a standard RF transceiver, is that the standard RF transceiver must incorporate a high Q filter in order to filter the adjacent channels. The necessity of a high Q filter becomes quite cumbersome when there is a need for standard and/or commercial off the shelf RF transceiver.
Moreover, previous art devices such as noise cancellation, interference cancellation, and regular channel filters are expensive solutions for leakages between adjacent channels.
A significant general limitation of currently available interference cancellation devices, is that they are using a small fraction of the transmitted signal with a phase correction to cancel the leakages between the adjacent channels. Therefore, interference cancellation is an expensive and sensitive solution because of the need to control the phase and amplitude of the correcting signal by means of vector modulators or phase shifters, which are sensitive and expensive components. In addition, the implementation of interference cancellation is problematic because of the parasitic capacitors which require evaluation and compensation.
Recently, several devices, based on circular polarized antennas have been disclosed. In these disclosures there is no reference to the novel embodiment of the present invention.
There is substantial prior art regarding circular polarized antennas. However, none of the following indicated prior art refers to highly isolated, circular polarized, multiple, independent, closely mounted antennas, or includes the important feature of recessed corner patches, or includes the important feature of the novel channel filter of the present invention.
Prior art includes various teachings of using recessed corners. In PCT International Patent Application Publication No. WO/9908337A1, issued to Hansen Per Steinar et al., there is disclosed a method of using a microwave antenna comprises a dielectric substrate with an emitter element and a feed line to the emitter element, and on the substrate underside there is a ground plane for the feed line. A separate ground plane for the emitter element is arranged at a larger distance from the substrate, and the two ground planes are interconnected electrically. The feed line ground plane is shaped with a tuning section extending somewhat in underneath the emitter element, and the tuning section is connected to the rest of the feed line ground plane via a transition section. However, there is no description or suggestion for using more than one recessed corner patch. Moreover, Hansen Per Steinar et al. provides no description or suggestion relating to determining and/or using two complementary recessed corners patches, and no description or suggestion relating to using the novel channel filter of the present invention.
In U.S. patent application Ser. No. 20040189532A1, issued to Nakano Hisamatsu et al., there is disclosed an antenna apparatus comprises a dielectric substrate, a radiation element buried in the dielectric substrate, and a feeding lead connected to the radiation element and extracted outward from the dielectric substrate. The dielectric substrate is covered with a conductor cover except an exposed portion left on a front surface thereof. The conductor cover comprises a side wall portion extending in a thickness direction of the radiation element and covering all side surfaces of the dielectric substrate, and a hood portion extending from an upper edge of the side wall portion and covers a part of the front surface of the dielectric substrate. The hood portion has a trapezoidal or a rectangular shape. Here too, there is no description or suggestion relating to using more than one recessed corner patch. Moreover, Nakano Hisamatsu et al. provides no description or suggestion relating to determining and/or using two complementary recessed corners patches, and no description or suggestion relating to using the novel channel filter of the present invention.
In U.S. Pat. No. 6,326,923, issued to Shigihara Makoto, there is disclosed a miniaturized circular polarized microstrip antenna that employs a dielectric substrate having a large relative dielectric constant so that a desired resonance frequency and a desired axis ratio are obtained. In a circular polarized wave microstrip antenna having a nearly square dielectric substrate with a nearly square patch electrode formed on one surface thereof, and a ground electrode formed on almost the whole of another surface thereof, triangular first notches and serving as retraction-separation elements are respectively formed 135 and 315 degrees with respect to a direction toward a feeding point from the center of the patch electrode, which is defined as 0, and within the first notch, a first adjustment electrode extending outwardly from an edge of the patch electrode is formed. On the other hand, a triangular second notch is formed 45 degrees with respect to a direction toward the feeding point from the center of the patch electrode, which is defined as 0, and within the second notch, a second adjustment electrode extending outwardly from an edge of the patch electrode is formed. Here too, there is no description or suggestion relating to using more than one recessed corner patch. Moreover, Shigihara Makoto provides no description or suggestion relating to determining and/or using two complementary recessed corners patches, and no description or suggestion relating to using the novel channel filter of the present invention
In U.S. Pat. No. 4,866,451, issued to Chen Chun-Hong, there is disclosed a circular polarization technique and a microstrip array antenna implementing this technique. Using four microstrip radiating elements with proper phasing of the excitation in a 2×2 array configuration, the technique averages out the cross-polarized component of the radiation, generating circular polarization of high purity. The technique is broadband and capable of dual-polarized operation. The resultant 2×2 array can be used either independently as a circular polarization radiator or as the building subarray for a larger array. Here too, there is no description or suggestion relating to using more than one recessed corner patch. Moreover, Chen Chun-Hong provides no description or suggestion relating to determining and/or using two complementary recessed corners patches, and no description or suggestion relating to using the novel channel filter of the present invention.
To date, the inventor is unaware of prior art teaching of adjacent channels operation based on downconverting the input signal to an IF signal, filtering the IF signal, and upconverting the filtered IF signal to the original frequency.
To one of ordinary skill in the art there is thus a need for, and it would be highly advantageous to have a method and device for adjacent channels operation based on downconverting the input signal to an IF signal, filtering the IF signal, and upconverting the filtered IF signal to the original frequency.
Moreover, there is a need for, and it would be highly advantageous to have a standard RF transceiver which does not incorporate a high Q filter, in order to reduce costs and improve time-to-market.
It is also desirable to have adjacent channels featuring the novel channel filter of the present invention and a highly isolated, circular, polarized smart antenna featuring recessed corner patches.